JP7314752B2 - PHOTOELECTRIC CONVERSION ELEMENT, READING DEVICE, IMAGE PROCESSING DEVICE, AND METHOD FOR MANUFACTURING PHOTOELECTRIC CONVERSION ELEMENT - Google Patents

Description

The present invention relates to a photoelectric conversion element, a reader, an image processing apparatus, and a method for manufacturing a photoelectric conversion element.

In recent years, awareness of document security has increased, and among other things, the needs for guaranteeing the originality of documents and authenticity determination are increasing.

Patent Document 1 discloses an invisible information reading technology that embeds invisible information (e.g., infrared (IR) information) in a document and reads it with invisible light (e.g., infrared light) to ensure originality, determine authenticity, and prevent counterfeiting.

Further, Patent Document 2 discloses an RGB+IR simultaneous reading technology for reading an RGB image and an IR image at the same time without reducing productivity by configuring a 4-line image sensor in which IR pixels are added to normal RGB pixels.

However, according to the conventional simultaneous reading of RGB+IR, there is a problem that the RGB image and the IR image cannot be read at the same time with a good S/N, because noise resistance is not taken into consideration. This is mainly because no consideration is given to dealing with the charge accumulated in the IR pixels.

The present invention has been made in view of the above, and an object of the present invention is to provide a photoelectric conversion element, a reading device, an image processing apparatus, and a method for manufacturing a photoelectric conversion element that can simultaneously read a visible image and an invisible image while preventing a decrease in S/N.

In order to solve the above-described problems and achieve the object, the present invention provides a first pixel column having a plurality of first light receiving portions arranged along one direction and having first pixels which receive at least a first wavelength within the visible region, a second pixel column having a plurality of second light receiving portions arranged along the one direction and having second pixels which receive at least a second wavelength outside the visible region, and a second pixel column provided in the first pixel column and transmitting signals from the first pixels to a subsequent stage. and a second pixel circuit provided in the second pixel column for transmitting the signal from the second pixel to a subsequent stage, wherein the second pixel circuit is provided in a region near the second pixel column., arranging dummy pixel rows imitating pixel rows and pixel circuits at both ends of a sensing region including at least the second pixel row;It is characterized by

According to the present invention, it is possible to read a visible image and an invisible image at the same time while preventing a decrease in S/N in the invisible region, which has low sensitivity and is particularly difficult to deal with.

FIG. 1 is a diagram illustrating an example configuration of an image forming apparatus according to a first embodiment. FIG. 2 is a cross-sectional view exemplifying the structure of the image reading unit. FIG. 3 is a diagram showing a configuration example of a light source. FIG. 4 is a diagram showing the spectrum of the light source. FIG. 5 is a diagram showing an example of spectral sensitivity characteristics of an image sensor. FIG. 6 is a diagram illustrating the layer structure of a color filter. FIG. 7 is a diagram schematically showing the configuration of an image sensor. FIG. 8 is a diagram showing the pixel circuit configuration of the image sensor. FIG. 9 is a diagram schematically showing the physical structure of a pixel circuit of an image sensor. FIG. 10 is a diagram showing an arrangement example of RGB/IR signal lines. FIG. 11 is a diagram showing the effect of reducing crosstalk from visible light signals. FIG. 12 is a block diagram showing electrical connection of each part constituting the image reading section. FIG. 13 is a diagram schematically showing the physical structure of the pixel circuit of the image sensor according to the second embodiment; FIG. 14 is a diagram schematically showing the configuration of an image sensor according to a third embodiment; FIG. 15 is a diagram schematically showing the configuration of an image sensor according to a fourth embodiment; FIG. 16 is a diagram schematically showing the configuration of an image sensor according to a fifth embodiment;

Exemplary embodiments of a photoelectric conversion element, a reader, an image processing apparatus, and a method for manufacturing a photoelectric conversion element will be described below in detail with reference to the accompanying drawings.

(First embodiment)
FIG. 1 is a diagram showing an example configuration of an image forming apparatus 100 according to the first embodiment. In FIG. 1, an image forming apparatus 100, which is an image processing apparatus, is generally called a multifunction machine having at least two functions out of a copy function, a printer function, a scanner function, and a facsimile function.

The image forming apparatus 100 has an image reading section 101 and an ADF (Automatic Document Feeder) 102 which are reading devices, and an image forming section 103 below them. In order to explain the internal configuration of the image forming unit 103, the external cover is removed to show the internal configuration.

The ADF 102 is a document support unit that positions a document, whose image is to be read, at a reading position. The ADF 102 automatically conveys the document placed on the placing table to the reading position. The image reading unit 101 reads a document conveyed by the ADF 102 at a predetermined reading position. Further, the image reading unit 101 has a contact glass as a document supporting portion on which a document is placed on its upper surface, and reads the document on the contact glass as a reading position. Specifically, the image reading unit 101 is a scanner having a light source, an optical system, and a CMOS image sensor inside, and reads the reflected light of the document illuminated by the light source with the image sensor through the optical system.

The image forming section 103 has a manual feed roller 104 for manually feeding recording paper, and a recording paper supply unit 107 for supplying recording paper. The recording paper supply unit 107 has a mechanism for feeding recording paper from a multistage recording paper feed cassette 107a. The supplied recording paper is sent to the secondary transfer belt 112 via the registration roller 108 .

The toner image on the intermediate transfer belt 113 is transferred in the transfer unit 114 to the recording paper conveyed on the secondary transfer belt 112 .

The image forming unit 103 includes an optical writing device 109, tandem image forming units (Y, M, C, and K) 105, an intermediate transfer belt 113, the secondary transfer belt 112, and the like. An image written by the optical writing device 109 is formed as a toner image on the intermediate transfer belt 113 by an image forming process by the image forming unit 105 .

Specifically, the image forming unit (Y, M, C, K) 105 has four rotatable photoreceptor drums (Y, M, C, K), and around each photoreceptor drum is provided an image forming element 106 including a charging roller, a developing device, a primary transfer roller, a cleaner unit, and a static eliminator. An image forming element 106 functions on each photoreceptor drum, and an image on the photoreceptor drum is transferred onto an intermediate transfer belt 113 by each primary transfer roller.

The intermediate transfer belt 113 is stretched by a driving roller and a driven roller in a nip between each photosensitive drum and each primary transfer roller. The toner image primarily transferred onto the intermediate transfer belt 113 is secondarily transferred onto the recording paper on the secondary transfer belt 112 by the secondary transfer device as the intermediate transfer belt 113 runs. The recording paper is conveyed to the fixing device 110 by running the secondary transfer belt 112, and the toner image is fixed on the recording paper as a color image. After that, the recording paper is discharged to a paper discharge tray outside the machine. In the case of double-sided printing, the reversing mechanism 111 reverses the front and back of the recording paper, and the reversed recording paper is sent onto the secondary transfer belt 112 .

Note that the image forming unit 103 is not limited to forming an image by the electrophotographic method as described above, and may form an image by an inkjet method.

Next, the image reading unit 101 will be described.

FIG. 2 is a cross-sectional view showing an exemplary structure of the image reading unit 101. As shown in FIG. As shown in FIG. 2, the image reading unit 101 includes a sensor substrate 10 having an image sensor 9 that is a photoelectric conversion element, a lens unit 8, a first carriage 6 and a second carriage 7 in a main body 11. FIG. The image sensor 9 is a reduction optical system sensor, such as a CMOS image sensor. The image sensor 9 includes a large number of photodiodes (PD) 92 (see FIGS. 6, 7, etc.) forming pixels. The first carriage 6 has a light source 2 which is an LED (Light Emitting Diode) and a mirror 3 . The second carriage 7 has mirrors 4,5. Further, the image reading unit 101 has a contact glass 1 and a reference white plate 13 on its upper surface.

In the reading operation, the image reading unit 101 emits light upward from the light source 2 while moving the first carriage 6 and the second carriage 7 from the standby position (home position) in the sub-scanning direction (direction A). The first carriage 6 and the second carriage 7 form an image of the reflected light from the document 12 on the image sensor 9 via the lens unit 8 .

When the power is turned on, the image reading unit 101 reads reflected light from the reference white plate 13 to set a reference. That is, the image reading unit 101 moves the first carriage 6 directly below the reference white plate 13, turns on the light source 2, and forms an image of the reflected light from the reference white plate 13 on the image sensor 9, thereby adjusting the gain.

Here, the light source 2 will be described in detail.

FIG. 3 is a diagram showing a configuration example of the light source 2. As shown in FIG. As shown in FIG. 3, the light source 2 includes a visible light source 2a (white) for reading a visible image (visible information) and an infrared (IR) invisible light source 2b for reading an invisible image (invisible information) alternately arranged in one lamp.

Here, FIG. 4 is a diagram showing the spectral spectrum of the light source 2. In FIG. FIG. 4(a) shows the spectrum of the visible light source 2a, and FIG. 4(b) shows the spectrum of the invisible light source 2b (IR). 4(a) and 4(b) show emission spectra of the visible light source 2a (white) and the invisible light source 2b (IR) in the case of LEDs.

Incidentally, in reading the visible/invisible image, any image information may be selectively read in the end. Therefore, in the present embodiment, the emission wavelength of the light source 2 is switched between visible and invisible. The switching of the light source 2 is performed by the light source driving section 24 (see FIG. 12) according to the control of the control section 23 (see FIG. 12).

As described above, by switching between the visible light source 2a (white) and the invisible light source 2b (IR), visible/invisible image reading can be realized with a simple configuration.

In the present embodiment, an example in which the visible light source 2a (white) and the invisible light source 2b (IR) are alternately arranged in one lamp is shown, but the present invention is not limited to this. Further, even when the visible light source 2a (white) and the invisible light source 2b (IR) are configured in one lamp, it is not necessarily limited to this as long as the light source 2 can illuminate the subject, such as arranging them in a plurality of rows.

Next, the image sensor 9 will be described in detail.

Here, FIG. 5 is a diagram showing an example of spectral sensitivity characteristics of the image sensor 9. As shown in FIG. The image sensor 9 of this embodiment is a general Si (silicon) image sensor such as a CMOS image sensor. Common Si image sensors also have quantum sensitivity in the infrared (IR) region of 800-1000 nm. Therefore, by using the wavelength region of the infrared (IR) region of 800 to 1000 nm as the invisible light region, it can be used in a highly sensitive state and the S / N of the invisible image can be increased, so the light utilization efficiency of the invisible image can be increased. That is, it is possible to realize an apparatus for reading an invisible image with a simple configuration.

Further, the image sensor 9 of the present embodiment has a configuration in which the RGB pixels respectively configured by the PDs 92 are composed of only RGB monochromatic color filters, and no IR cut filter is used. Therefore, as shown in FIG. 5, the spectral sensitivity characteristic of the image sensor 9 is R+IR/G+IR/B+IR/IR.

In this embodiment, reading of RGB will be described, but the reading is not limited to this, and may be CMY, OGV, or the like. Further, it is not always necessary to be a full-color pixel array, and pixel arrays that receive visible light, such as G only, or monochrome without a color filter, may be used.

FIG. 6 is a diagram illustrating the layer structure of a color filter. Conventionally, an RGB pixel has a two-layer structure in which an RGB monochromatic filter and an IR cut filter (IRC) are laminated. The IR pixel has a single-layer structure in which only a color filter that transmits only IR is mounted.

On the other hand, as shown in FIG. 6, the image sensor 9 of the present embodiment has a single-layer structure in which only RGB monochromatic color filters 91R, 91G, and 91B are mounted in the RGB pixels, which are the PDs 92. FIG. Further, the image sensor 9 of the present embodiment has a single-layer structure in which only the color filter 91IR that transmits only IR is mounted in the IR pixel that is the PD 92 .

Color filters are generally applied by spin coating. As shown in FIG. 6, all the color filters 91R, 91G, 91B, and 91IR are configured with the same number of layers and the thicknesses of the color filters 91R, 91G, 91B, and 91IR are made uniform, thereby suppressing coating unevenness of the color filters 91R, 91G, 91B, and 91IR, and preventing a decrease in yield.

In this way, by using only the monochromatic color filters 91R, 91G, 91B, and 91IR to configure the RGB pixels to have photosensitivity also to IR and not using an IR cut filter, the color filters 91R, 91G, 91B, and 91IR have a single-layer configuration, and an increase in cost can be suppressed.

Conventionally, the IR cut filter is added to remove the IR component mixed in the RGB pixels, but by removing the IR component mixed in the RGB pixels in the subsequent image processing unit 25 (see FIG. 12) using the IR pixel signal, it is possible to easily obtain the same effect as the IR cut filter.

By the way, the signal amount of IR pixels is a fraction of that of RGB pixels. This is because, as shown in FIG. 5, the Si image sensor has lower quantum sensitivity in the invisible infrared (IR) region than in the visible region. Therefore, signal attenuation, which has no effect on RGB pixels, becomes a problem in the case of IR pixels with relatively small signal amounts.

In addition, the long-distance transfer of electric charge makes it susceptible to external noise. The influence of such external noise is also greater for IR pixels than for RGB pixels.

As described above, compared to RGB pixels, IR pixel signals are more susceptible to signal attenuation and extraneous noise, and the S/N reduction becomes a problem. Therefore, it is important to deal with signals (charges) output from pixels. In particular, in the case of a sensor for a reduction optical system in which the pixel size is about 1/10 smaller than that of a contact image sensor, it is essential to deal with the signal (charge) output from the pixel.

Here, FIG. 7 is a diagram schematically showing the configuration of the image sensor 9. As shown in FIG. As shown in FIG. 7, the image sensor 9 is a 4-line pixel configuration image sensor in which IR pixels are added to RGB pixels.

As shown in FIG. 7, the image sensor 9 has a light receiving portion column of R pixels (R pixel column 90R: third pixel column), a light receiving portion column of G pixels (G pixel column 90G: first pixel column), a light receiving portion column of B pixels (B pixel column 90B: fourth pixel column), and a light receiving portion column of IR pixels (IR pixel column 90IR: second pixel column) each extending along the main scanning direction x. The image sensor 9 has an R pixel row 90R, a G pixel row 90G, a B pixel row 90B, and an IR pixel row 90IR in this order along the sub-scanning direction y.

The R pixel row 90R has a plurality of R pixel light receiving portions (third light receiving portions) 94R arranged at a constant pitch in a line along the main scanning direction x. The R pixel row 90R receives red light from the light source 2 . The light-receiving portion 94R of the R pixel includes a PD 92 that configures the R pixel (third pixel) and a pixel circuit (PIX_BLK) 93 that is a third pixel circuit that performs charge-voltage conversion.

In this embodiment, hereinafter, the area where the PD 92 is located is called a pixel area (PIX), and the area where the pixel circuit (PIX_BLK) 93 is located is called a non-pixel area (Non-PIX).

The G pixel row 90G has a plurality of G pixel light receiving portions (first light receiving portions) 94G arranged at a constant pitch in a line along the main scanning direction x. The G pixel row 90G receives green light from the light source 2 . The G-pixel light-receiving unit 94G includes a PD 92 that constitutes a G-pixel (first pixel) and a pixel circuit (PIX_BLK) 93 that is a first pixel circuit for charge-to-voltage conversion.

The B pixel row 90B has a plurality of B pixel light receiving portions (fourth light receiving portions) 94B arranged at a constant pitch in a line along the main scanning direction x. The B pixel row 90B receives blue light from the light source 2 . The light-receiving portion 94B of the B pixel includes a PD 92 that constitutes the B pixel (fourth pixel) and a pixel circuit (PIX_BLK) 93 that is a fourth pixel circuit that performs charge-voltage conversion.

The IR pixel row 90IR has a plurality of IR pixel light receiving portions (second light receiving portions) 94IR arranged in a row along the main scanning direction x at a constant pitch. IR pixel array 90 IR receives infrared light from light source 2 . The light receiving portion 94IR of the IR pixel includes a PD 92 that forms an IR pixel (second pixel) and a pixel circuit (PIX_BLK) 93 that is a second pixel circuit for charge-voltage conversion.

Note that the R pixel row 90R, G pixel row 90G, B pixel row 90B, and IR pixel row 90IR are only identified by color filters as described above, and circuit portions such as the PD 92 and pixel circuit (PIX_BLK) 93 are the same. Therefore, it can be regarded as a continuous pattern of four pixel columns.

In this embodiment, as shown in FIG. 7, the image sensor 9 has a pixel circuit (PIX_BLK) 93 at a position adjacent to the pixel region (PIX) having the PD 92 . A signal (charge) photoelectrically converted by the PD 92 is output to the adjacent pixel circuit (PIX_BLK) 93 and subjected to charge-voltage conversion. A signal (SIG) converted into a voltage is independently output to a subsequent stage for each pixel. This makes it possible to minimize the distance for transferring charges from each PD 92 to the pixel circuit (PIX_BLK) 93 and prevent signal attenuation and noise superimposition.

In particular, in the IR pixel column 90IR, the pixel circuit (PIX_BLK) 93 is arranged adjacent to the pixel region (PIX) having the PD 92 that constitutes the IR pixel. For example, if the distance between the IR pixel and the pixel circuit (PIX_BLK) 93 is close to the distance corresponding to several pixels, signal attenuation and noise superposition can be prevented. Here, the neighborhood refers to, for example, a distance of several pixels wide, and in this case, it is a sufficiently short distance to suppress signal attenuation and noise superimposition.

Further, as shown in FIG. 7, in the image sensor 9, the interval between the visible light pixel row (R pixel row 90R, G pixel row 90G, B pixel row 90B) and the IR pixel row 90IR is an integer line. In the example shown in FIG. 7, the line interval is 2 lines, but considering that the pixel circuit (PIX_BLK) 93 is arranged in the vicinity of the PD 92, 2 lines is the minimum number of integer lines, which is the arrangement that is most likely to prevent positional deviation. This makes it possible to prevent positional deviation (image mismatch) between the visible image and the invisible image. A line is a unit obtained by converting one main scanning line into a physical distance. Hereinafter, in the image sensor of this embodiment, one line will be described as a physical distance in units of sub-scanning widths of pixels (PD).

In addition, in the present embodiment, the IR pixel is described as an example of the invisible light pixel. Since a general-purpose silicon semiconductor can be used by using the IR region, it can be configured at low cost. However, the present invention is not limited to this, and the effect of the present invention can be obtained by using other non-visible light pixels having low sensitivity to visible light pixels such as UV.

FIG. 8 is a diagram showing the pixel circuit configuration of the image sensor 9. As shown in FIG. As shown in FIG. 8, the image sensor 9 has a PD 92, a floating diffusion (FD) 95, a reset transistor (Tr1) 96, a transfer transistor (Tr2) 97, and a source follower (SF) 98 in the R pixel light receiving portion 94R, the G pixel light receiving portion 94G, the B pixel light receiving portion 94B, and the IR pixel light receiving portion 94IR. In FIG. 8, T is the control signal for the transfer transistor (Tr2) 97, RS is the control signal for the reset transistor (Tr1) 96, and VDD is the power supply for the transistors 96 and 97. FIG.

As shown in FIG. 8, light incident on the image sensor 9 is photoelectrically converted by the PD 92 . The charges photoelectrically converted are transferred to the floating diffusion (FD) 95 via the transfer transistor (Tr2) 97 . The charge transferred to the FD 95 is converted into a voltage signal and output to the subsequent stage via a source follower (SF) 98 . After outputting the signal, the FD 95 has its charge reset by a reset transistor (Tr1) 96 .

By the way, as described above, when the image processing unit 25 (see FIG. 12) in the subsequent stage uses the IR pixel signal to perform correction for removing the IR component mixed in the RGB pixel, it is desirable that the IR component included in the RGB pixel and the IR component in the IR pixel are equal.

FIG. 9 is a diagram schematically showing the physical structure of the pixel circuit of the image sensor 9. As shown in FIG. As shown in FIG. 9, the image sensor 9 has the same configuration and physical structure (size and arrangement) of pixel circuits (PIX_BLK) 93 including Tr1 (RS) 96, Tr2 (T) 97, and FD 95 for RGB pixels and IR pixels. Although SF98 is not specified in FIG. 9, it can be considered that FD95 corresponds. Accordingly, by aligning the IR characteristics of the RGB pixels and the IR characteristics of the IR pixels, it is possible to easily remove the IR component (invisible component) from the RGB image (visible image).

FIG. 10 is a diagram showing an arrangement example of RGB/IR signal lines.

As described with reference to FIG. 5, IR pixels have lower sensitivity than RGB pixels, so the signal amount is smaller than that of RGB pixels. Therefore, the effect on noise is greater than that of RGB pixels. Further, although the RGB/IR signal lines are evenly arranged in FIG. 8, crosstalk between signals becomes a problem due to parasitic capacitance between the signal lines. In particular, when the IR pixels receive crosstalk from other RGB signals, the effect is great and poses a problem in terms of image quality.

FIG. 10A is an enlarged view of the signal line (portion output from the pixel circuit (PIX_BLK) 93 to the subsequent stage) shown in FIG. The signal lines 99R, 99G, and 99B of the RGB pixels are separated by a distance a, but the signal line 99B of the B pixels and the signal line 99IR of the IR pixels are separated by a distance b (a<b). Thus, by making the distance between the signal line 99B of the B pixel and the signal line 99IR of the IR pixel longer than the distance between the signal lines 99R, 99G, and 99B of the RGB pixels, crosstalk from the RGB pixels to the IR pixel signals can be reduced.

FIG. 10(b) is an example in which shield lines 80 are arranged on both sides of the IR pixel signal line 99IR in contrast to FIG. 10(a). In this case, noise (crosstalk) components from RGB pixel signals (especially B pixel signals) are absorbed by the shield, so crosstalk from RGB pixel signals to IR pixel signals can be suppressed.

The shield line 80 can be easily implemented as long as it is a low-impedance line, and may be a power supply (VDD), a ground (GND), or a signal line equivalent to the power supply or GND.

FIG. 11 is a diagram showing the effect of reducing crosstalk from visible light signals. FIG. 11(a) shows a case where the signal line 99IR for the IR pixel is spaced at the same intervals as the signal lines 99R, 99G, 99B for the RGB pixels. FIG. 11(a) shows how the amount of change in the fall of the signal of the adjacent B pixel crosstalks with the IR pixel.

On the other hand, FIG. 11(b) shows the case where the configuration shown in FIG. 10(a) is used. As shown in FIG. 11(b), since the signal line 99IR of the IR pixel is separated by more than the distance between the RGB pixels, crosstalk is reduced.

Also, FIG. 11(c) shows a case where the configuration shown in FIG. 10(b) is used. As shown in FIG. 11(c), the shield line 80 completely absorbs the crosstalk component, thereby suppressing the crosstalk to the IR pixels.

FIG. 12 is a block diagram showing the electrical connection of each part forming the image reading unit 101. As shown in FIG. As shown in FIG. 12, the image reading unit 101 includes a signal processing unit 21, an SD (shading) correction unit 22 as a signal correction unit, a control unit 23, a light source driving unit 24, and an image processing unit 25 in addition to the image sensor 9 and the light source 2 described above.

The light source 2 is configured for visible/infrared (IR), as described above. The light source driving section 24 drives the light source 2 .

The signal processing section 21 has a gain control section (amplifier), an offset control section, and an A/D conversion section (AD converter). The signal processing unit 21 performs gain control, offset control, and A/D conversion on image signals (RGB) output from the image sensor 9 .

The control unit 23 selectively controls the visible image mode or the IR image mode, and controls settings of the light source driving unit 24 , the image sensor 9 , the signal processing unit 21 and the SD correction unit 22 . The control unit 23 functions as reading control means that selectively controls the first reading operation and the second reading operation.

In the first reading operation, shading correction using first reference data is performed on data obtained by reading an object in the visible light region. In the second reading operation, shading correction using second reference data is performed on data obtained by reading the subject in the invisible light region.

The SD correction unit 22 has a line memory and performs shading correction. The shading correction is performed by normalizing the main scanning distribution, such as variations in sensitivity of the image sensor 9 for each pixel and unevenness in the amount of light, using the reference white plate 13 .

The image processing unit 25 executes various image processing. For example, the image processor 25 includes an IR component remover 26 that is an invisible component remover. The IR component removing unit 26 removes the IR component (second wavelength component) mixed in the RGB pixels using the IR pixel signal. As a result, it is possible to acquire a high-quality invisible image (IR image) that prevents a decrease in S/N while suppressing deterioration in color reproduction of a visible image (RGB image).

As described above, according to the present embodiment, by providing the pixel circuit (PIX_BLK) 93 adjacent to the IR pixel, the transfer distance of photoelectrically converted signals (charges) can be minimized and long-distance transfer can be eliminated. As a result, attenuation of IR pixel signals and superimposition of external noise can be avoided, and an RGB image and an IR image can be simultaneously read while preventing S/N reduction in the infrared (invisible) region, which has low sensitivity and is particularly difficult to deal with.

In addition, by forming the pixel circuit (PIX_BLK) 93 adjacent to the pixel area not only for the IR pixel but also for the RGB pixel, it is possible to simultaneously perform invisible IR reading and full-color reading (here, RGB) while preventing a decrease in S/N.

Further, by arranging the pixel circuits (PIX_BLK) 93 adjacent to each pixel, the charge transfer distance can be minimized for each pixel, so that the S/N reduction can be prevented for all pixels.

(Second embodiment)
Next, a second embodiment will be described.

In the first embodiment, the IR characteristics of the RGB pixels and the IR characteristics of the IR pixels are aligned to facilitate correction. However, the second embodiment differs from the first embodiment in that the structure of the pixel circuit (PIX_BLK) 93 of the IR pixel is different from that of the pixel circuit (PIX_BLK) 93 of the RGB pixels. Hereinafter, in the description of the second embodiment, the description of the same portions as those of the first embodiment will be omitted, and the portions different from those of the first embodiment will be described.

FIG. 13 is a diagram schematically showing the physical structure of the pixel circuit of the image sensor 9 according to the second embodiment. FIG. 9 shows a configuration in which the IR characteristics of the RGB pixels and the IR characteristics of the IR pixels are aligned to facilitate correction.

Therefore, in the present embodiment, as shown in FIG. 13, the configuration and physical structure (size, arrangement) of the pixel circuit (PIX_BLK) 93 of the IR pixel are made different from the configuration and physical structure (size, arrangement) of the pixel circuit (PIX_BLK) 93 of the RGB pixel, thereby increasing the sensitivity of the IR pixel. FIG. 13 shows the physical structure of the PD 92 and pixel circuit (PIX_BLK) 93, and differs from FIG. 9 in that the IR pixel PD 92 and pixel circuit (PIX_BLK) 93 are arranged at a deeper position.

Here, it is known that the quantum sensitivity of silicon is higher (easily absorbed) at a position closer to the silicon surface as the wavelength is shorter, and is higher at a deeper position in the silicon as the wavelength is longer. That is, infrared light is more likely to undergo photoelectric conversion at a deeper position in silicon than RGB light, that is, the photosensitivity is increased (wavelength dependence of silicon quantum sensitivity in the depth direction).

Therefore, in the image sensor 9 shown in FIG. 13, the PD 92 is extended to a deeper position in IR pixels than in RGB pixels. Thereby, the IR light receiving sensitivity can be increased.

In the image sensor 9 shown in FIG. 13, the pixel circuit (PIX_BLK) 93 including Tr1 (RS) 96, TR2 (T) 97, and FD 95 is also configured to a deeper position in consideration of the generation and movement of charges at a deeper position.

As described above, according to the present embodiment, by arranging the PD 92 of the IR pixel and the pixel circuit (PIX_BLK) 93 at a deeper position than the PD 92 of the RGB pixel and the pixel circuit (PIX_BLK) 93, it is possible to reduce the decrease in the light receiving sensitivity in the invisible range.

(Third Embodiment)
Next, a third embodiment will be described.

The third embodiment differs from the first and second embodiments in that dummy pixel rows are arranged above and below the R pixel row 90R, G pixel row 90G, B pixel row 90B, and IR pixel row 90IR. Hereinafter, in the description of the third embodiment, the description of the same parts as those of the first to second embodiments will be omitted, and the parts different from those of the first to second embodiments will be described.

FIG. 14 is a diagram schematically showing the configuration of an image sensor 9 according to the third embodiment.

In the semiconductor process, it is generally known that the end region of a continuous pattern changes its characteristics more than other regions. This is because the semiconductor process is affected by the peripheral pattern (design) in manufacturing, and the edge region of the continuous pattern becomes the boundary of the pattern. In the case of the image sensor 9 of this embodiment, the R pixel row 90R or the IR pixel row 90IR having the configuration shown in FIG. 7 serves as a pattern boundary, and the characteristics tend to change with respect to the other G pixel row 90G and B pixel row 90B.

Therefore, as shown in FIG. 14, the image sensor 9 of the present embodiment additionally arranges a dummy pixel row 90dummy imitating a pixel row and a pixel circuit at the end of the sensing region including at least the IR pixel row 90IR (here, above the R pixel row 90R and below the IR pixel row 90IR). The R pixel column 90R and the IR pixel column 90IR become part of the continuous pattern due to the addition of the dummy pixel column 90dummy, and are no longer boundary pixels of the pattern. Therefore, the peripheral pattern conditions are uniform for R/G/B/IR, and it is possible to reduce the characteristic difference between pixels (colors).

Note that the continuity of the circuit pattern is important for the dummy pixel row 90dummy shown in FIG. 14, and any color filter may be used. This is because the manufacturing process generally includes a step of applying a color filter after the step of generating circuits.

As described above, according to the present embodiment, it is possible to match the characteristics between colors regardless of the visible/invisible range.

(Fourth embodiment)
Next, a fourth embodiment will be described.

The fourth embodiment differs from the first to third embodiments in that the IR pixels are arranged away from the RGB pixels. Hereinafter, in the description of the fourth embodiment, the description of the same portions as those of the first to third embodiments will be omitted, and the portions different from those of the first to third embodiments will be described.

FIG. 15 is a diagram schematically showing the configuration of an image sensor 9 according to the fourth embodiment.

In FIG. 10, reference was made to crosstalk between pixel signals, that is, electrical crosstalk. By the way, as described in the third embodiment, since the quantum sensitivity of silicon differs in the depth of photoelectric conversion depending on the wavelength of received light, crosstalk due to charges between pixels may become a problem. In particular, since infrared light is photoelectrically converted at a deeper position, if control by an electric field is not sufficient, photoelectrically converted electric charges float inside the silicon and mix into the pixels of other colors (PD92), causing crosstalk.

Therefore, as shown in FIG. 15, the image sensor 9 of this embodiment has a configuration in which the IR pixels are kept away from the RGB pixels. The example shown in FIG. 15 is an example in which only the IR pixel row 90IR is spaced from the B pixel row 90B by four lines, which is wider than the RGB pixel interval. In this embodiment, the continuity of the circuit pattern is maintained by inserting a dummy pixel row 90dummy imitating a pixel row and a pixel circuit between the B pixel row 90B and the IR pixel row 90IR.

As described above, according to the present embodiment, it is possible to reduce the influence of crosstalk due to inter-pixel charges from IR pixels to RGB pixels.

In the example shown in FIG. 15, the pixel row adjacent to the IR pixel row 90IR is arranged as the B pixel row 90B, but by configuring the pixel rows so that the wavelength difference (B wavelength: about 450 nm, IR wavelength: about 800 nm) of light incident on the adjacent pixel row is maximized, the difference in the depth position where photoelectric conversion is performed can be maximized, so the influence of charge crosstalk can be reduced to the maximum.

(Fifth embodiment)
Next, a fifth embodiment will be described.

The fifth embodiment differs from the first to fourth embodiments in that a plurality of (AD converters) (ADCs) are provided after and near the pixel circuit (PIX_BLK) 93 . Hereinafter, in the description of the fifth embodiment, the description of the same portions as those of the first to fourth embodiments will be omitted, and the portions different from those of the first to fourth embodiments will be described.

FIG. 16 is a diagram schematically showing the configuration of an image sensor 9 according to the fifth embodiment.

As shown in FIG. 16, the image sensor 9 according to the present embodiment includes IR pixels in addition to RGB pixels, and pixel circuits (PIX_BLK) 93 are arranged in the vicinity of the pixels (PIX). Furthermore, the image sensor 9 includes a plurality of ADCs 70 in the rear stage and vicinity of the pixel circuit (PIX_BLK) 93 .

Note that the neighborhood is a distance within which each signal can be transmitted within a predetermined time, for example, the difference in distance from each pixel (PD 92) processed by the ADC 70 to the ADC 70 does not differ by an order of magnitude (or more than two digits). That is, the image sensor 9 has an extremely short analog path by arranging the ADC 70 near the pixel (PD 92) and the pixel circuit (PIX_BLK) 93. FIG.

The image sensor 9 also includes an LVDS (Low-Voltage-Differential-Signals) 71 that is a differential interface. The image sensor 9 also includes a timing generator (TG; Timing Generator) 72 . A timing generator 72 supplies a control signal to each block to control the operation of the entire image sensor 9 .

The image sensor 9 according to this embodiment performs A/D conversion with the ADC 70 in the same chip, and transmits image data to the subsequent stage with the LVDS 71 .

As described above, according to the present embodiment, the ADC 70 is arranged near the pixel (PD 92) and the pixel circuit (PIX_BLK) 93, and A/D conversion is performed within the same chip, so that even when the IR pixel is added, the operation speed is increased, and a high-quality image with a good S/N can be generated.

Although the pixel circuit (PIX_BLK) 93 and the ADC 70 are connected in FIG. 16, an arbitrary circuit such as a PGA may be arranged between them. Also, the ADC 70 may be any ADC, such as a parallel processing type using a plurality of ADCs, a single pipelined type, or the like. Further, although processing blocks, a data mapping section, and the like are provided between the ADC 70 and the LVDS 71, they are omitted in FIG.

In each of the above-described embodiments, an example in which the image processing apparatus of the present invention is applied to a multifunction machine having at least two functions out of a copy function, a printer function, a scanner function, and a facsimile function will be described.

Furthermore, in each of the above-described embodiments, an example in which the reading device or image processing device of the present invention is applied to a multifunction machine has been described, but the present invention is not limited to this, and can be applied to applications in various fields such as inspection in the FA field.

Further, the reading device or the image processing device of the present invention can also be applied to a bill reading device for the purposes of distinguishing bills and preventing forgery.

2 light source 9 photoelectric conversion element 26 invisible component removing unit 70 AD converter 80 shield line 90R third pixel row 90G first pixel row 90B fourth pixel row 90IR second pixel row 90dummy dummy pixel row 91R, 91G, 91B, 91IR color filter 92 first pixel, second pixel, third pixel, fourth pixel 93 first pixel pixel circuit, second pixel circuit, third pixel circuit, fourth pixel circuit 94R third light receiving portion 94G first light receiving portion 94B fourth light receiving portion 94IR second light receiving portion 100 image processing device 101 reading device 103 image forming portion

JP 2005-143134 A Japanese Patent No. 6101448

Claims (20)

a first pixel row having a plurality of first light receiving portions arranged along one direction and having first pixels that receive at least a first wavelength in the visible region;
a second pixel row having a plurality of second light receiving portions arranged along the one direction and having second pixels that receive at least a second wavelength outside the visible range;
a first pixel circuit provided in the first pixel column and transmitting a signal from the first pixel to a subsequent stage;
a second pixel circuit provided in the second pixel column and transmitting a signal from the second pixel to a subsequent stage;
with
The second pixel circuit is provided in a region near the second pixel, and dummy pixel rows imitating pixel rows and pixel circuits are arranged at both ends of a sensing region including at least the second pixel row,
A photoelectric conversion device characterized by: The second pixel circuit is provided in a region adjacent to the second pixel,
2. The photoelectric conversion element according to claim 1, characterized in that: The first pixel circuit is provided in a region adjacent to the first pixel,
3. The photoelectric conversion element according to claim 1, wherein: a third pixel row having a plurality of third light receiving portions arranged along the one direction and having third pixels that receive at least a third wavelength in a visible region different from the first wavelength;
a fourth pixel row having a plurality of fourth light receiving portions arranged along the one direction and including fourth pixels that receive at least a fourth wavelength within a visible region different from the first wavelength and the third wavelength;
a third pixel circuit provided in a region adjacent to the third pixel and transmitting a signal from the third pixel to a subsequent stage;
a fourth pixel circuit provided in a region adjacent to the fourth pixel and transmitting a signal from the fourth pixel to a subsequent stage;
The photoelectric conversion element according to any one of claims 1 to 3, characterized by comprising: increasing the distance between the output line of the second pixel circuit and the output line of the first pixel circuit, the output line of the third pixel circuit, or the output line of the fourth pixel circuit with respect to the distance between the output line of the first pixel circuit, the output line of the third pixel circuit, or the output line of the fourth pixel circuit;
5. The photoelectric conversion element according to claim 4, characterized in that: placing shield lines on both sides of the output line of the second pixel circuit;
The photoelectric conversion element according to any one of claims 1 to 5, characterized in that: the second pixel column receives infrared light;
The photoelectric conversion element according to any one of claims 1 to 6, characterized in that: wherein the first pixel column receives green light, the third pixel column receives red light, and the fourth pixel column receives blue light;
5. The photoelectric conversion element according to claim 4, characterized in that: The distance between the second pixel row and the pixel row that receives the wavelength in the visible region other than the second pixel row is an integral multiple of the physical distance in units of sub-scanning widths of pixels.
The photoelectric conversion element according to any one of claims 1 to 8 , characterized in that: the first pixel column or the third pixel column or the fourth pixel column also receives the second wavelength;
5. The photoelectric conversion element according to claim 4, characterized in that: The color filters included in the first pixel row, the second pixel row, the third pixel row, and the fourth pixel row are all configured with the same number of layers.
5. The photoelectric conversion element according to claim 4, characterized in that: The second pixel row and the pixel rows other than the second pixel row that receive wavelengths in the visible region have the same physical structure.
The photoelectric conversion element according to any one of claims 1 to 11 , characterized in that: The second pixel row and the pixel rows other than the second pixel row that receive wavelengths in the visible region have different physical structures,
The photoelectric conversion element according to any one of claims 1 to 11 , characterized in that: The distance between the second pixel row and the pixel row that receives the wavelength in the visible region other than the second pixel row is longer than the distance between the pixel rows that receive the wavelength in the visible region other than the second pixel row.
5. The photoelectric conversion element according to claim 4, characterized in that: The second pixel row is arranged next to a pixel row that receives light having a maximum wavelength difference from the second wavelength.
15. The photoelectric conversion element according to any one of claims 1 to 14 , characterized in that: An AD converter is provided after and in the vicinity of the first pixel circuit, the second pixel circuit, the third pixel circuit, and the fourth pixel circuit,
5. The photoelectric conversion element according to claim 4, characterized in that: a light source that emits visible light and invisible light;
The photoelectric conversion element according to any one of claims 1 to 16 , which receives reflected light of light emitted from the light source;
A reading device comprising: An invisible component removal unit that removes the second wavelength component contained in the first pixel row, the third pixel row, or the fourth pixel row,
18. The reader according to claim 17 , characterized by: a reader according to claim 17 or 18 ;
an image forming unit;
An image processing device comprising: a first pixel column having a plurality of first light-receiving portions arranged along one direction and having first pixels receiving at least a first wavelength within the visible range; a second pixel column having a plurality of second light-receiving portions aligned along the one direction and having second pixels receiving at least a second wavelength outside the visible range; and a second pixel circuit for transmitting a signal from the second pixel to a subsequent stage, comprising:
The second pixel circuit is provided in a region near the second pixel row, and dummy pixel rows imitating the pixel row and the pixel circuit are arranged at both ends of the sensing region including at least the second pixel row,
A method for manufacturing a photoelectric conversion element, characterized by:

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